“I don’t really believe in this stuff,” says Cathy Goldsmith, “but I feel like sometimes he sends me answers when I’m stuck.” Goldsmith, the associate publishing director of Random House’s Golden Books Young Readers Group, was the last editor to work with Theodor Geisel, a.k.a. Dr. Seuss, before he died in 1991. In 2013, when his widow found the sheets of a complete book, What Pet Should I Get?, Goldsmith...